Keoshkerian et al., U.S. Pat. No. 6,469,094 describes a process for the preparation of polymeric particulate materials employing a free radical polymerizable monomer, a free radical initiator and a stable free radical compound wherein the process includes a first bulk polymerization where controlled initiation and limited or partial monomer polymerization is accomplished for the purpose of preparing a prepolymer mixture followed by a second stage miniemulsion polymerization where substantially complete monomer polymerization is accomplished. There is a need, which the present invention addresses, for new free radical polymerization processes that produce polymer particles with a covalently bound charged group on the particle surface. Such polymer particles with the functional group are advantageous since they are amenable to further manipulation such as aggregation/coalescence in chemical toner processes.
Exemplary polymerization processes are described in the following:
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The present invention is accomplished in embodiments by providing a process comprising:
heating to a first polymerization temperature a first mixture comprising a first free radical polymerizable monomer, a first free radical initiator, and a first stable free radical compound to polymerize only a portion of the first monomer, resulting in a prepolymer composition;
shearing a second mixture including the prepolymer composition, a continuous phase liquid, and a stabilizing compound to create a miniemulsion; and
heating to a second polymerization temperature the miniemulsion to form polymeric particles, wherein there is added to the second mixture, the miniemulsion, or both the second mixture and the miniemulsion at any time prior to the formation of the polymeric particles a second free radical initiator, a second free radical polymerizable monomer, and an optional second stable free radical compound, wherein at least one of the second initiator and the second monomer includes a functional group, wherein the polymeric particles each includes a compound with the functional group covalently bound and with the functional group disposed on the particle surface.
There is also provided in embodiments a process comprising:
heating to a first polymerization temperature a first mixture comprising a first free radical polymerizable monomer, a first free radical initiator, and a first stable free radical compound to polymerize only a portion of the first monomer, resulting in a prepolymer composition, wherein the first mixture prior to heating is free of water;
shearing a second mixture including the prepolymer composition, water, and a stabilizing compound to create a miniemulsion; and
heating to a second polymerization temperature the miniemulsion to form polymeric particles, wherein there is added to the second mixture, the miniemulsion, or both the second mixture and the miniemulsion at any time prior to the formation of the polymeric particles a second free radical initiator, a second free radical polymerizable monomer, and an optional second stable free radical compound, wherein the second initiator includes a first functional group and the second monomer includes a second functional group, wherein the polymeric particles each includes a compound with the first functional group and the second functional group which are covalently bound and wherein the first functional group and the second functional group are disposed on the particle surface.